Fuse



Sept 21, 1943- H. A. TRlPLET-r 2,329,957

FUSE

Filed June 28, 1957 Patented Sept. 2l,

FUSE

Hugh A. Triplea, wumette, nl., assigner to Schweitzer & Conrad, Inc.,Chicago, IIL, a corporation of Delaware Application June 28, 1937,Serial No. 150,667

14 Claims.

My invention relates, generally, to fuse devices and it has particularrelation to replaceable fuse links adapted to be mounted in a fuse tubeor housing of the expulsion type.

In the copendingapplication of Allan Ramsey, Serial No. 559,846, filedAugust 28, 1931, and assigned to the assignee of this application, nowPatent No. 2,091,452, a fuse housing arranged for receiving areplaceable fuse link and adapted for mounting in a box is illustratedand described. The box is formed of a suitable insulating material, suchas porcelain, and it is adapted to be mounted on a cross arm or the likeand is provided with terminals to which line conductors may beconnected.

The fuse housing or tube itself is arranged to be detachably mounted ona cover that is hinged to the box and serves to close the same. The fusetube is formed of suitable insulating material and it has ferrules atits ends from which spring wire contact fingers project for contactengagement with stationary terminals in the box.

Different types of replaceable fuse links are illustrated in thisapplication. Generally these links comprise a terminal that is arrangedto be connected to a movable terminal inside, of the fuse tube to whichis attached a coil tension spring that serves to bias the movableterminal toward the normally closed end of the fuse tube.

. The fuse link is mounted adjacent the open end of the fuse tube and isprovided with a flexible lead that serves as a connection to theterminal adjacent the open end of the fuse tube. Between the terminaland flexible lead of the replaceable fuse link a fusible element, forexample, a silver wire, is provided to electrically interconnect the twoparts. In order to relieve this fusible element of the stress that wouldotherwise be imposed thereon by the coil spring in the fuse tube, astrain wire mechanically interconnects these two parts. The fusible andstrain elements are disposed between a pair of generallysemicylindrically shaped pieces of insulation, such as cork, which aresecurely held together and in position by a suitable tube, such as awaterproofed paper tube.

On flow of suflicient current to melt the fusible element the currentflow is transferred to the strain element which is immediately fused:and releases the movable terminal in the fuse tube for movement towardthe closed end under the biasing force of the coil spring. 'Ihe arc isdrawn at the open end of the fuse tube, thereby permitting the rapidevolution of gases generated thereby without building up dangerouspressures in the fuse tube. By drawing the arc in the fuse tube towardthe closed end, advantage may be taken of the expulsion action of thedevice and arc extinguishing vapors or gases that are evolved from theinner lining of the fuse tube to rapidly extinguish the arc.

The object of the present invention, generally stated, is to provide animproved form of replaceable fuse link over that shown in the copendingapplication of Ramsey which will be efficient in operation and which canbe readily and economically manufactured and installed.

An important object of my invention is to improve the arc extinguishingcharacteristics of a replaceable fuse link.

Another object of my invention is to provide non-vegetable material in afuse link which is replaceable therewith and which is capable ofevolving an arc extinguishing medium on the blowing of the fuse linkthat will assist in extinguishing the arc.

Still another object of my invention is to place a mass of inorganic areextinguishing material in a spring tensioned renewable fuse link in suchposition that it will be acted upon by the heat of the arc and evolvetherefrom a gaseous medium, the combined action of the spring tensionand the gaseous medium evolved from the inorganic arc extinguishingmaterial serving to effect rapid interruption of relatively small faultcurrents. i

Other objects of my invention will, in part, be obvious and, in part,appear hereinafter.

Accordingly my invention is disclosedgin the embodiment thereof shown inthe accompanying drawing and it comprises the features of construction,combination of elements and arrangement of parts which will beexemplified in the construction hereinafter set forth and the scope ofthe application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of myinvention reference may be had to the following detailed descriptiontaken in connection with the accompanying drawing in4 which:

Figure 1 is a longitudinal sectional view of a fuse housing or tube thatis adapted to receive the novel fuse link of the present invention;

Figure 2 is a longitudinal sectional view of the fuse link shown inFigure l, the terminal and flexible lead being shown in elevation;

Figure 3 is a longitudinal sectional view, similar to that shown inFigure 2, but taken at night angles thereto for the purpose of showingthe arrangement of the fusible and strain element;

Figure 4 is a detailed sectional view, at an enlarged scale, taken alongthe line 4--4 of Fig- IU is provided with a. metal ferrule I2 that issecured in position by screws I3 and I4 which project into suitablythreaded apertures, as shown.

With a View to providing for connecting the ferrule I2 to a terminal(not shown), it is provided with two pairs4 of arms I5, only one of eachbeing shown, which are apertured at their outer ends for receivingtransverse pins, such as the pin I6. Contact engagement with thestationary terminal isprovided by flexible spring wires I1, the outerends of which are looped around the pin I6 and spaced apart by suitablewashers I8. The ferrule I2 is provided with a hook I9 for mounting it onthe cover (not shown) of the fuse box, as will bel readily-understood.

The upper enld of the ferrule I2 is threaded for receiving a cap screw22. On its underside the cap screw 22 is provided with an integrallyformed boss 23 having a helical groove 24 for receiving one end of atension coil spring 25. The other end of the coil spring '25 is disposedin a suitable helical groove 26 in a movable terminal 21. The cap screw22 and the movable terminal 21 are provided with socket portions 28 and29 respectively for :receiving therein the ends of a flexible conductor30. It will be observed now that the cap screw 22 closes the upper endof the fuse tube Ill and that electrical connection between the ferruleI 2 and the movable terminal 21 is provided by the flexible conductor 30so that the spring 25 is not called upon to conduct current;Furthermore, it will be noted that the coil spring 25 serves to bias themovable terminal 21 from the lower open end of the fuse tube I towardthe upper and closed end.

Adjacent the lower open end of the fuse tube I 0 a second ferrule 33 isprovided. This ferrule is of split construction and is arranged to beclamped to the fuse tube I Il by means of suitable bolts 34. The mannerof electrically connecting the ferrule 33 to the correspondingstationary terminal (not shown), is similar to that for ferrule I2. Theferrule 33 is provided with two pairs of arms 35, only one of each beingshown,

' and pins, such as the pin 36, extend transversely therebetween forreceiving the looped outer ends of flexible spring wire fingers 31,these looped outer ends being spaced apart by suitable washers 38.

With a viewto electrically interconnecting the movable terminal 21 andthe ferrule 33, a replaceable fuse link, shown generally at 40, isprovided. As shown, the fuse link 40 is positioned at the lower open endof the fuse tube I0 so that the gases generated on blowing thereof maybe readily vented to the atmosphere. At one end the fuse link 40 lisprovided with a fuse link terminal 4I and at the other Iend with aflexible lead 42. The fuse link terminal 4I is preferably forme-d byflattening a short length of copper tubing for 'a purpose that will bepresently apparent. The

flexible lead 42 is preferably formed by a. relatively thin copper strapthat is tinned. The link terminal 4I is placed on a attened portion 43of the movable terminal 21 and over a stud 44 on which is threaded a nut45. The stud 44 may be secured in position in the movable terminal 21 bya pin 46. It Will be observed that the exible lead 42 extends out of thelower end of the fuse tube Ill and over a stud 41 that is threaded intothe ferrule 33. A nut 48 is provided for securing the end of theflexible lead 42 in position and in proper contact engagement with theferrule 33.

With the exception of the fuse link 40, the apparatus just described andshown in Figure 1 of the drawing is fully described in the copendingapplication of Ramsey, hereinbefore referred to, and, therefore, afurther description thereof will not be set forth herein.

The details of construction of the replaceable fuse link 4I) areillustrated more clearly in Figures 2, 3, and 4 of the drawing. As thereshown. the fuse link terminal 4I is provided with a suitable aperture 5Ifor fitting over the stud 44 on the movable terminal 21. Likewise, theflexible lead 42 is provided with anaperture 52, preferably oblong inshape, for tting over the stud 41. The flexible lead 42 is provided witha tail 53 that may be grasped by the han'd for pulling the fuse link 40attached to the movable terminal 21 to the position shown in Figure l ofthe drawing and positioning the end over the stud 41. A series of smallholes 54 is pro-vided to facilitate breaking oi of the tail 53 when thedevice has been re-fused.

'I'he fuse link terminal 4I and the iiexible lead 42 are electricallyinterconnected by a fusible element 55, preferably in the form of asilver wire or it may be composed of zinc or tin. It will be understoodthat different sizes and lengths of fusible element 55 may be provideddepending upon the ampere rating of the fuse link. In order to relievethe fusible element 55 of the stress that would otherwise be imposedthereon by the coil spring 25, a strain elem-ent 56, formed preferablyof high tensile strength wire such as nickelchromium, is provided formechanically interconnecting the fuse link terminal 4 I and the flexiblelead 42. 'Ille strain element 56 is formed into a generallyrectangularly shaped loop with the upper ends 51 turned inwardly andcrossed as illustrated. The ends 51 of the strain element 56 and theupper end of the fusible element 55 are disposed inside of the linkterminal 4I which is then collapsed thereon to the position shown.Indentations 58 are made in the fuse link terminal 5I, as shovm, inorder to secure the ends 51 of the strain element 56 in position. Asleeve 59, formed preferably of tinned copper, and initially in tubularshape, surrounds the lower ends of the fusible and strain elements 55and 56 and the upper end of the flexible lead 42. Suitable indentations60 are provided in the sleeve 59 for securely fastening the lower end ofthe strain element 56 in place. It will be noted that the copper tubingforming the terminal 4I and the upper end of the flexible lead 42 withthe sleeve 59 therearound form relatively infusible terminals for thefusible and strain elements 55 and 56, thereby confining thevaporization of metal on blowing substantially to these two elements.

The fusible and strain elements 55 and 56 are encased in a housing thatis formed by a pair of generally semi-cylindrically shaped members 65that are preferably formed of cork. These two members 65 are secured inposition by a sleeve 66 that may be formed of paper that has b'eensuitably water-proofed. v

In the copending application of Ramsey, hereinbefore referred to, themembers 65 are solid throughout their entire length. I have found thatthe arc extinguishing ability of the fuse link I may be improved byproviding cavities, such as the cavities 61, in these members 65 andthen filling the same with a suitable arc extinguishing material 68,such as calcium carbonate or lithium carbonate in powdered form. Whenthe cavities 61, which may be formed by drilling the members 66 with asuitably shaped drill, are filled with the arc extinguishing material66, the fusible and strain elements 55 and 56 are embedded therein. Inthis position the arc that is formed on blowing of the fusible andstrain elements immediately contacts the arc extinguishing ma terial 68and, due to the heat of the arc. an arc extinguishing medium is evolvedtherefrom that is capable of materially assisting in extinguishingthearc. When the filling 68 is of calcium carbonate or lithiumcarbonate, carbon dioxide is evolved which is capable of assisting inextinguishing the arc. It will be observed that the arc extinguishingmaterial 68 is kept from contact with the atmosphere by the members 65and the sleeve 66.

Under certain operating conditions it has been possible, by the use ofthe arc extinguishing material 68 in the fuse link 40 itself, tomaterially decrease the number of cycles of alternating current duringwhich an arc is maintained once it is formed with respect to the numberof cycles that are required to extinguish the same when this material isnot used. That is, when the members 65 are made solid, as is the case inthe copending application of Ramsey, considerably more time is requiredto extinguish the arc than is the case when these members are providedwith the cavities 61 and they are filled with arc extinguishing materialsuch as calcium carbonate or lithium carbonate. This is particularlytrue in the interruption of relatively small fault currents because ofthe combined action of the spring 25 in extending the arc drawn onblowing of the fusible and strain elements 55 and 56 and the gaseousmedium such as carbon dioxide, that is evolved from the arcextinguishing material With a view to preventing one of the members 65from being expelled while the other is not under certain relatively lowfault current conditions. a washer Il having a suitable centrallylocated slotted opening is placed around the flexible lead 42immediately below the members 65 and is secured in position by a cotterpin 12. On formation of an arc between the terminals of the fuse link 40the are extinguishin-g material 68 is retained in close proximitythereto, especially for low fault currents, and it is possible to takefull advantage of it which might not be the case if one of the members65 were expelled.

It will be obvious that certain changes may be made in the aboveconstruction and that different embodiments of the invention may be madewithout departing from the scope thereof. Therefore, it is intended thatall matter contained in the foregoing description or shown in theaccompanying drawing shall be interpreted as illustrative and not in alimiting sense.

I claim as my invention:

l. A replaceable fuse link adapted for mounting under tension in a fusehousing comprising,

in combination, a pair of terminal members, a fusible elementelectrically interconnecting said terminal members, non-vegetable arcextinguishing material carried by the fuse link and replaceabletherewith from which by action of an arc drawn on blowing of saidfusible element a gaseous arc extinguishing medium is evolved, and astrain element mechanically interconnecting said terminal members forrelieving said fusible element of stress otherwise imposed thereon bythe tension in the fuse housing.

2. A replaceable fuse link adapted for mounting under spring tension ina fuse housing comprising, in combination; a terminal, a flexible lead,a fusible element electrically interconnecting said terminal and saidflexible lead, a strain element mechanically interconnecting saidterminal and said flexible lead for relieving said fusible element ofstress otherwise imposed thereon by the spring tension in the fusehousing, and inorganic arc extinguishing material carried by the fuselink, replaceable therewith and closed to the atmosphere from which byaction of an arc drawn on blowing of said fusible and strain elements agaseous arc extinguishing medium is evolved.

3. A replaceable fuse link adapted for mounting under spring tension ina fuse housing comprising, in combination, a pair of relativelyinfusible terminals, a flexible lead connected to one of said terminals,a fusible element electrically inter-connecting said terminals, a strainelement mechanically interconnecting said terminals for relieving saidfusible element of stress otherwise imposed thereon by the springtension in the fuse housing, Aand a filling of powder embedding saidfusible and strain elements and adapted to evolve an arc extinguishingmedium due to the heat of-the arc formed on blowing of the fuse link. il

4. A replaceable fuse link adapted for mounting under tension in a. fusehousing comprising,l in combination, a pair of terminal members. afusible element electrically interconnecting said terminal members, amass of lithium carbonate carried by the fuse link and replaceabletherewith for evolving carbon dioxide on blowing of said fusible elementto assist in extinguishing the arc, and a strain element mechanicallyinterconnecting said terminal members for relieving said fusible elementof stress otherwise imposed thereon by the tension in the fuse housing.

5. A replaceable fuse link adapted for mounting under tension in a fusehousing comprising, in combination, a pair of terminal members, afusible element electrically interconnecting said terminal members, amass of calcium carbonate carried by the fuse link and'replaceabletherewith for evolving carbon dioxide on blowing of said fusible elementto assist in extinguishing the arc, and a strain element mechanicallyinterconnecting said terminal members for relieving said fusible elementof stress otherwise imposed thereon bythe tension in the fuse housing.

6. A replaceable fuse link adapted for mounting under spring tension ina fuse housing comprising, in combination, a terminal, a flexible lead,a fusible element electrically interconnecting said terminal and saidflexible lead, a strain element mechanically interconnecting saidterminal and said flexible lead for relieving said fusible element ofstress otherwise imposed thereon by the spring tension in the fusehousing, and a mass of lithium carbonate adjacent said fusible andstrain elements for evolving said fusible and strain elements forevolving carbon dioxide due to the heat of the arc formed on blowing ofthe fuse link for assisting in extinguishing the arc.

8. A replaceable fuse link adapted for mounting under tension in a fusehousing comprising, in combination, a pair of terminal members, afusible element electrically interconnecting said terminal members, astrain element mechanically interconnecting said terminal members forrelieving said fusible element of the stress otherwise imposed thereonby the tension in the fuse housing, a sleeve of insulation surroundingsaid fusible and strain elements, and extending in overlapping relationwith the adjacent portions of said terminal members, and a mass ofinorganic arc extinguishing material within said sleeve of insulationand adjacent said fusible and strain elements from which by action of anarc a gaseous arc extinguishing medium is evolved.

9. A replaceable fuse link adapted for mounting under spring tension ina fuse housing comprising in combination, a terminal, .a flexible lead,a fusible element electrically interconnecting said terminal and saidiiexible lead, a strain element mechanically interconnecting saidterminal and said exible lead for relieving said fusible element ofstress otherwise imposed thereon by the spring tension in the fusehousing, a sleeve of insulation surrounding said fusible and strainelements and extending in overlapping relation with the adjacentportions of said terminal and flexible lead, and a mass of powdered arcextinguishing material within said sleeve of insulation from which byaction of an arc a gaseous arc extinguishing medium is evolved.

housing, a sleeve of insulation surrounding said fusible and strainelements and extending in overlapping relation with the adjacentportions of said terminal members, and a mass of lithium carbonatewithin said sleeve of insulation and4 adjacent said fusible and strainelements for evolving carbon dioxide due to the heat of the arc formedon blowing of the fuse link for assisting in extinguishing the arc.

11. A replaceable fuse link adapted for mounting under spring tension ina fuse housing comprising, in combination, a terminal, a flexible lead,a fusible element electrically interconnecting said terminal and saidflexible lead, a strain element mechanically interconnecting said teryminal and said flexible lead for relieving said fusible element ofstress otherwise imposed thereon by the spring tension in the fusehousing, a sleeve of insulation surrounding said fusible and extendingin overlapping relation with the adjacent portions of said lead, and amass of lithium arc formed on blowing of the fuse link for assisting inextinguishing the arc.

12. A replaceable fuse link adapted for mounting under tension in a fusehousing comprising, in combination, a pair of terminal members, afusible element electrically interconnecting said terminal members, astrain element mechanically interconnecting said terminal members forrelieving said fusible element of the stress othering said terminal andsaid flexible lead, a strain element mechanically interconnecting saidterminal and said flexible lead for relieving said of stress otherwiseimposed thereon by the spring tension in the fuse hous- HU GH A.TRIPLE'IT.

